Inaccurate Thermostat

If you checked the wall with other thermometers and they read the same as the thermostat, then it could be the heat that is coming from the chase that makes the thermostat read a little high.

The fan stops and starts but the burners are functioning

What is the quick remedy

Cure for the problem.

Make a spacer for behind the thermostat. This will leave a air space between the thermostat and the chase allowing the thermostat to only read to room air temperature. Just use small pieces of wood or as we always did short pieces of 1/2 inch plastic electric tubing or plastic water pipe (plastic or wood is used to prevent and short circuits from forming like might happen with metal pipe if the back of the thermostat has any of the printed circuits on it or other wiring. Then we just used longer screws to pass through the thermostat then the spacer then into the wall. Just tighten enough to hold thermostat on wall you do not want to bow or deform the plastic part of the thermostat.

Next make sure that the hole in the wall the thermostat cable passes through is caulked tight around the wire so no air from the chase can interfere with the thermostat temperature reading or activation of the thermostat.

This has been done before and it works well to cure this type of problem. You will probably find out after completing the above cure your thermostat will not need any calibration at all.

The thermostat reads lower than the one in the kitchen

The thermostat has a gap and the hole is sealed and the thermostat show lower than the one in the kitchen

Yes thermostats need to be calibrated, its called cycles per hour(on new digital thermostats), same thing as a heat anticipator on old mercuray thermostats. The instructions should indeed tell how to set this. Most likely, if you have a 80 % furnace, it will need to be set at 5 cycle per hour(usually factory setting), if you have a 90+ effeciency furnace, you will most likey have to change the cycle rate to 3 cycles per hour.

Read all instructions very carefully, you are looking for cycles.

He is talking about the temperature that the thermostat shows like in a thermometer not how long the unit is running I believe.

Calibration or anticipator settings are used when the furnace runs to long or to short overshooting or undershooting the set point of the thermostat. Anticipator settings will not change the base point of the thermometer reading for room temp. Now some thermostats are have the base line temp changeable but that is a different set of instrutions and that will be addressed differently in the thermostat manual. This feature is not universal and not all thermostats offer this setting adjustmant.

The thermostat is directly attached to a to hot or to warm chase causing the thermostat to read incorrectly. The wire can be caulked but without the spacers it still will not work correctly if the wall it is mounted to is to cold or hot as compared to the surrounding temperature. Been there done that but many times no one wants to fix it correctly since it takes some skill or additional labor to mount it to the chase with the spacers.

This tip was given to me 40 years ago by Honeywell at one of there trade seminars and it will solve these kind of problems.

Thanks everyone. Indeed, it maintains the set temperature VERY well, unfortunately, as HVAC indicated, it is misreading the temperature.

The hole the wire runs through is actually quite large, perhaps 2" square, so I am sure a fair amount of warm air is hitting the thermostat.

HVAC, your suggestion to use spacers sounds perfect. I will use the spacer to make sure I cover over the hole left by the installer. How thick of a spacer should I use? 1"? More? Less?

Also, would it be better to either mount the thermostat on a different wall(possible but a bit of work) or get a wireless thermostat(expensive)?

Thanks!